A lot of it is personal preference. There is people that run both ways without issues.
Benifits to sump: Cleaner, more live rock if you choose, cheato place, refuge, more water capacity, better place to dose, more consistant tempuratures...
Benifits to sumpless: Less headache and cheaper...
I was happy with out a sump and now that my sump is set up I am still just as happy
